1. Field of the Invention
The invention relates to a measuring mechanism for wide-angle moving coil systems, consisting of a mount with a movable part, an inner and an outer pole ring and one or two magnets. The invention relates further to a method for assembling the parts.
2. Background of the Prior Art
With known measuring mechanisms of the initially described type, the movable part of the measuring mechanism can be mounted and balanced only inside the magnetic system. These operations, however, are a very great waste of time and impose a great burden on assembly personnel. Because of the simultaneous incorporation of heavy and highly sensitive parts in a single operating step, a further potential danger is that of damaging sensitive measuring mechanism pivots and bearings. To mechanize and/or economize on these operations is practically impossible.
A further drawback of these known measuring mechanisms is that the pole rings and magnets have to be screwed or bonded together in an expensive way. Because it is very expensive to insert bores or the like into permanent magnets, the screw coupling is extremely expensive.
A further difficult requirement is that the parts need to be arranged concentrically and for this purpose require adjustment. This operating stage is necessary because otherwise the scalar linearity of the measuring mechanism cannot be guaranteed. A mutual bonding of the parts requires considerably complex apparatus. Despite this complexity, however, usually the desired degree of concentricity is not reached and, further, cannot be corrected, which has detrimental effects. The above noted costs of final assembly of the measuring mechanism and its final adjustment must also be considered.
An object of the invention then is to provide a measuring mechanism for wide-angle moving coil systems, where together with an extensive reduction in production and assembly costs, the required concentricity of magnetic system components and, accordingly, the desired linearity of measuring mechanism readouts can be accomplished. Specific fabrication aims are a simplification of laborious assembly operations and avoidance of adjusting operations. These problems arise for the above noted wide-angle moving coil systems, where the pointer, and therewith the moving coil frame, must sweep a wide angle, e.g., of 250.degree.. In this case, the discussed problems of concentricity and linearity are substantially more difficult to manage than with so-called 90.degree.-instruments, i.e., where moving coil frame and pointer sweep only a 90.degree.-angle, and where part of the negative eccentricity effects produced on instrument linearity are cancelled. This is so because the coil at diametrically opposed positions dips twice into the magnetic field. But with so-called 250.degree. or wide-angle systems--in contrast with 90.degree.-systems--there is no compensation for momentary deviation effective at both coil sides.
As stated above, the present invention, as originally set forth in the parent application and as further described herein, relates to a measuring mechanism for wide-angle moving coil systems, comprising a mount with a movable part, a magnetic system with an inner and an outer pole ring and one or two magnets. For this purpose, it is suggested that a form-locking arrangement of the magnet or magnets and the pole rings relative to each other be provided in such a manner that the pole rings are mutually centered and fixed in this position in any direction, wherein each of both pole rings terminates in two arms or ends between which a slot or spacing is arranged, wherein, further, the internal space of the inner pole ring serving to receive the corresponding parts of the movable part, for example, a part of its moving coil frame, is accessible from the outside through the slot arranged between its arms. The width of the slot is dimensioned in such a way that the finished movable part can be moved with its parts through the slot in the internal space of the inner pole ring.
For the assembly of the magnetic system, it is further provided that one of the support arms of the measuring mechanism carrier belonging to the frame, preferably the support arm which is the upper support arm during assembly which carries the axle bearings, has external dimensions whose projection on the magnetic system slid onto the movable part is located between the arms or ends of the outer pole ring when this ring is in the appropriate pivoting position.
The measuring mechanism according to the parent application has been successful. A primary object of the present improvement resides in, while maintaining a wide angular deflection, for example, 250.degree., achieving a higher stability with the dimensions of the measuring mechanisms remaining the same, or even achieving smaller dimensions of the measuring mechanisms with the stability being the same.